1. Field of the Invention
This invention relates to electric rotating machines, and is more particularly directed to small electric devices, such as micromotors, which can be incorporated into miniaturized electronic apparatus, such as miniature tape players and the like.
2. Description of the Prior Art
Micromotors or other miniature DC motors are presently used in miniature electronic apparatus as an alternative to solenoid plungers and are employed, for example, in a small portable cassette tape recorder player to establish its mode.
Coventional micromotors are constructed as brush-type DC motors including a housing, with field permanent magnets disposed within the housing; a rotor constituted by a shaft, a wound armature, and a commutator affixed on the shaft; and a brush assembly formed of an end plate for closing off the housing, brushes, and a bearing for one end of the shaft.
Assembly of such a conventional micromotor tends to be troublesome, and does not lend itself to automation. More specifically, in carrying out assembly of the conventional micromotor, the rotor is fitted axially into the housing, and then the brush assembly is fitted over the shaft. Difficulties are often encountered in spreading the brushes while the brush assembly is slid axially into place. These difficulties hinder attempts to automate the assembly of the motor, and cause mass-production jigs for motor assembly to be complex and cumbersome.
Also, when the micromotor is to be used in place of a solenoid plunger, a screw or worm is included on the rotor shaft to engage a claw for carrying out axial longitudinal displacement. However, because of the axial assembly required for conventional micromotors, journal type bearings must be used, and such bearings are severely limited as to the maximum axial load which can be placed on the motor.
Accordingly, it has been desired to provide structure for an electric rotating machine which is easily adaptable to automated assembly, and which enables the machine to withstand increased axial loads.